The present invention relates to apparatus for connecting elements together, and for damping or absorbing relative motion occurring between such elements. More particularly, the invention relates to hydraulic engine mounts of the kind provided with external controls for neutralizing by damping or absorbing relative movements of predetermined amplitudes between an engine and the chassis of an automotive vehicle.
Automotive engines do not always run smoothly. For instance, particularly during starting, before reaching their proper operating temperature, internal combustion engines may rock considerably and run roughly. Such rough running performance is unpleasant to drivers, and it is detrimental to the vehicle generally. Attempts have, therefore, been made to provide engine mounts capable of damping or absorbing the high amplitudes characteristic of rough engine performance.
Hydraulic engine mounts have been used successfully to reduce the effects of rough or rocky engine performance by damping or absorbing and thus substantially neutralizing high amplitude movements, by varying the resiliency of the mounts as a function of particular engine running conditions.
Thus, published Japanese Patent Application No. 57/76340(A) discloses a hydraulic engine mount comprising a support connected to an anchor by means of an elastic wall member. Support, anchor and wall member enclose a chamber filled with a fluid. A further chamber of variable volume and also filled with a fluid, is connected to a first chamber by a passage or conduit which permits some exchange of fluid between the chambers to equalize pressure differentials. A partition member having a throttle hole is slidably mounted within a widened section of the conduit. When the support is subjected to vibrations or movements of low frequency and high amplitude, the elastic wall member is elastically deformed and the capacity of the further fluid chamber is changed causing a pressure differential in the fluid in the two chambers. The partition member, under such circumstances, is said to descend instantly and fluid excapes from the second chamber into the first chamber through a narrow throttle hole provided in the partition member. This results in some damping of the movement owing to the resistance of the viscous fluid flowing through the throttle hole. In case of high frequency and low amplitude movements, the partition member is said vertically to reciprocate by a change in the pressure in the fluid in the chambers to absorb such minor movements. While the device may offer limited relief from the effects of relative movements of high amplitude between an engine and a chassis, the effectiveness of the device is not only limited but it is in any event unpredictable. A variety of hydraulic engine mounts of this kind has become known. In praxi such mounts have not always performed satisfactorily for they have been found sometimes to transfer high amplitude movements between the elements connected by them.
It is, therefore, an object of the invention to provide an improved hydraulic engine mount. A more specific object of the invention resides in the provision of a hydraulic engine mount capable of absorbing, or at least damping, engine movements of high amplitude.
Another object of the invention is to provide a hydraulic engine mount having variable movement absorption capability.
Furthermore, the invention has as one of its objects the provision of a hydraulic engine mount the movement absorbing capability of which may be effectively controlled to suit particular running conditions of an internal combustion engine.
A further object of the invention resides in an improved hydraulic engine mount which may be controlled by external controls.